The present invention relates to continuous ink jet printing and, more particularly, to a means for preventing the eyelid of an ink jet printhead from sticking shut and not operating properly after a completed shutdown.
Current ink jet printing systems consist of a fluid system supporting one or more printheads. Typical ink jet printheads operate by forcing fluid through a droplet generator which contains an array of orifices, forming droplets of ink. The printhead is fully supported by the fluid system, controlling different solenoid valves and pumps to perform necessary functions for the printhead to operate reliably. These functions include cleaning, startup, and shutdown. One particular function, shutdown, provides a means to stop operation of the printhead and fluid system over an extended period of time and allow for returned operation. At shutdown, the ink floods the leads and the area around the orifices. Flushing fluid and/or ink then dries, leaving behind non-volatile components in the form of solids or gels. Upon subsequent startups, the failure to remove or redissolve all of this material in the orifice and gap between the orifice plate and charge plate creates disturbances in the shape or direction of the emerging jet.
In the existing art, continuous ink jet printheads have a component called an eyelid to catch ink droplets when starting up automatically. The eyelid typically has a rubber-like material for sealing, a heater, and operates in an open and close fashion to allow for printing. It has been seen that with some inks during an extend period of shutdown, days or weeks, residual ink left at the seal of the eyelid to the catcher can dry. This dried ink can impede or prevent the eyelid from opening at the subsequent start up, producing a failure.
It would be desirable, then, to have a improved reliable operation by solving the issue of failures in eyelid operation due to dried ink and ink fluid residues in between the eyelid seal and the catcher.
This need is met by the technique according to the present invention wherein by automatically actuating the eyelid during purge and dry states in the shutdown sequence, residual ink jet fluid is removed from the sealing surfaces, preventing it from essentially xe2x80x9cgluingxe2x80x9d the eyelid shut and causing a failure.
In accordance with one aspect of the present invention, a system and method are provided to improve reliability of operation for a continuous ink jet printer. This system and method is for preventing ink residue and purge fluid residue from impeding operation of an eyelid of a printhead in a continuous ink jet printing system, particularly at a seal region defined between the eyelid and the catcher. The eyelid is actuated to open at least once during purge and dry states of a shutdown sequence of the printhead. A vacuum is maintained on a catcher throat of the catcher to cause air to enter a gap between the catcher pan and the eyelid, whereby high velocity air moving through the gap removes residual ink jet fluid at the seal region on both the eyelid and the catcher pan.
It is an object of the present invention to provide a means to prevent the eyelid on an ink jet printer from sticking, due to dried ink or dried purge fluid, and causing a failure in operation of the printhead. It is another object of the present invention to provide a method of actuating the eyelid at different time intervals to flush and dry the eyelid seal and catcher of an ink jet printer, providing reliable operation after an extended period of down time.
Other objects and advantages of the present invention will be apparent from the following description and the appended claims.